1. Field of the Invention
The present invention relates to a signal processing technique for reducing blur of a moving image in a storage display device, such as a liquid crystal display device.
2. Description of the Related Art
Liquid crystal display devices including a liquid crystal panel have been used widely in various fields. The liquid crystal display device is one of storage display devices using storage display elements for respective pixels. The storage display device has a low-pass time-frequency characteristic having the lowered response in a high signal frequency domain. A moving image displayed by the liquid crystal display device may have blur according to the moving speed of an object included in the moving image. A moving image displayed by the storage display device may have blur, due to afterimage on the retinas when the human eyes observe an object moving on the storage display device.
A technique disclosed in Japanese Patent Laid-Open Gazette No. 2002-132220 has been proposed to solve this problem.
The proposed technique reads out image data of each frame in an original image, which is sequentially stored at a frame period into a frame memory, twice at a field period that is half the frame period, and generates two image signals of a first field and a second field. Display of an image expressed by the image signal of the first field and display of an image expressed by the image signal of the second field completes a displayed image corresponding to each frame of the original image. The image signal of the first field is generated by replacing image data on even-numbered horizontal lines among multiple horizontal lines included in the first field with black image data. The image signal of the second field is generated by replacing image data on odd-numbered horizontal lines among the multiple horizontal lines included in the second field with the black image data. In each pixel on a horizontal line in the resulting displayed image, a black image expressed by the black image data is displayed in a previous field, prior to display of an object image expressed by original image data in a current field. Namely each pixel on the horizontal line is reset from display of a previous object image to display of the black image, prior to display of a next object image. This eliminates the effects of the previously displayed image and thus reduces blur of the moving image.
This prior art technique replaces the image data in the pixels on half the horizontal lines included in each field with the black image data. Such replacement undesirably decreases the actual luminance of the displayed image to half the theoretical luminance of each frame image and thereby lowers the contrast of the displayed image.